A student says: "Crude oil is a compound. Fractional distillation breaks its molecules into simpler hydrocarbons. Each fraction contains one pure substance."
Evaluate each part of this explanation.
[4 marks]OCR Gateway GCSE Combined Science November 2021 Paper 10
5 questions on this paper's topics
27:001 of 5
A reaction uses the same solution concentration at 20 °C and 35 °C. A student explains the faster reaction at 35 °C by saying particles are larger and the activation energy has decreased.
Evaluate the explanation.
[4 marks]A student electrolyses concentrated aqueous potassium chloride using inert electrodes in a teacher-controlled demonstration with suitable ventilation. Potassium is more reactive than hydrogen.
.1
Predict the electrode products and explain the difference from molten potassium chloride.
[3 marks].2
Explain how charge is carried through the aqueous electrolyte and through the external metal wires.
[2 marks]Three repeated demonstrations with equal samples of a group 1 metal collect hydrogen volumes of 47, 49 and 48 cm³. A separate run collects 31 cm³ after the gas tube becomes loose.
.1
Calculate the mean volume from the three valid repeated demonstrations.
[3 marks].2
Explain why the low run cannot show that the metal was less reactive.
[2 marks]A trial compares conventional mining with bioleaching for the same mass of copper recovered. Mining causes 120 units of landscape disturbance and uses 900 units of energy; bioleaching causes 35 and uses 600. Bioleaching takes much longer and its leachate must be contained.
.1
Calculate the percentage energy saving using bioleaching compared with mining.
[2 marks].2
Evaluate the claim that bioleaching has no environmental disadvantages.
[3 marks]